This invention relates generally to positioning mechanisms, and more particularly, to a substrate positioning system facilitating the performing of certain processing on the substrate, such as ion implantation.
Robotic units and other positioning mechanisms are known for performing certain controlled tasks. With respect to mechanisms for assisting in ion implantation on a substrate, such as a semiconducting wafer, a mechanical scanning apparatus has been used in conjunction with ion implanters to ensure that ion beams incident on the substrate reach the whole surface area. The ion implanters typically scan the ion beam electrically in a first axis across the substrate surface and utilize the mechanical scanning apparatus to scan the substrate mechanically along a second axis perpendicular to the first. The mechanical scan is necessary due to the difficulty of electrically scanning the beam over a large area of the substrate while keeping the angle of incidence of the beam to the substrate surface constant. Additionally, the mechanical scan must move the substrate at a certain velocity and at the correct angle of incidence as to avoid ion dosage and substrate depth non-uniformities.
Nogami et al., in U.S. Pat. No. 5,003,183, describe a mechanism that swings a wafer through the beam by rotating its holder from the side. Although this mechanism maintains a constant impact point of the ion beam with the wafer tilted at an angle of incidence, the wafer rotation must be coordinated with the scan to avoid velocity variation across the wafer and resulting ion dosage variations.
Brune et al., in U.S. Pat. No. 5,229,615, describe a two-link robot arm for mechanically scanning a wafer. This device requires the coordination of three rotary axes to maintain the angle of incidence at a constant value as the wafer is scanned, thus adding additional complexity of motion.
Thus, what is desired is a substrate positioning system that can accurately move a substrate to desired positions for performing certain processing thereon while having a reduced complexity of motion. In ion implantation, the system should mechanically scan the wafer through the ion beam at a constant angle of incidence while maintaining the ion dosage reaching the wafer surface at relatively constant values.
It is a feature of the present invention to provide a substrate positioning system to facilitate the performing of certain processing on the substrate, such as ion implantation. It is another feature to provide such a system with rotatable members synchronized to form a robotic unit to efficiently and accurately move the substrate to a desired range of motion. It is yet another feature to provide such a system with a base movable linearly along an axis such that the system maintains a constant distance of travel for an ion beam incident on the substrate as the rotatable members travel in a curved path. It is yet another feature of the present invention to provide such a system where the rotatable members simultaneously rotate to maintain a substantially constant incident angle of the substrate relative to the ion beam. It is yet another feature of the present invention to provide such a system that is easy to use, simple in operation, and particularly well suited for the proposed usages thereof.
The substrate positioning system of the present invention comprises a linkage rotatably mounted to a base and an end effector member rotatably mounted to the linkage and configured for supporting a substrate. Means is provided to rotate the linkage and the member simultaneously as a robotic unit to move the substrate to a desired y-axis and z-axis location to facilitate performing certain processing on the substrate.
In another aspect, the processing performed on the substrate involves ion implantation. A chamber is provided into which an ion beam is entered, the ion beam configured to scan over the width of a substrate along an x-axis. Within the chamber is the linkage attached at a first rotary axis to the base and the end effector member attached at a second rotary axis to the linkage, the linkage and end effector member forming a substrate holder to position the substrate. A drive unit is mechanically connected to the linkage to scan the end effector and held substrate through the ion beam substantially in a z-axis direction. Because the end effector member rotates about the second rotary axis as the linkage rotates about the first rotary axis, a substantially constant angle of incidence of the ion beam on the substrate is maintained. The system can be further configured with the base being movable along the y-axis such that the system maintains a constant distance of travel for the ion beam incident on the substrate as the linkage and end effector member travel in a curved path.
Other advantages and components of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, which constitute a part of this specification and wherein are set forth exemplary aspects of the present invention to illustrate various features thereof.